1. Field of the Invention
The invention relates to a method of making a conductive thermoplastic composition containing at least one dispersed phase polymer with a continuous phase polymer and at least one conductivity imparting agent wherein the bulk resistivity of the composition is at least partially determined by the particle size of the dispersed phase within the continuous phase. The thermoplastic composition preferably comprises a compatibilized blend of at least one polyphenylene ether resin, at least one polyamide resin, and at least one conductivity imparting agent, and optionally, one or more of impact modifiers, stabilizers, antioxidants, lubricants, and fillers. In one embodiment, this invention provides a method of controlling the bulk resistivity of a compatibilized blend of at least one polyphenylene ether resin and at least one polyamide resin, wherein the polyphenylene ether resin is a dispersed phase and wherein the method comprises varying the compatibilizing agent content and/or the level of level of copolymers between the polyphenylene ether resin and polyamide resin and/or the dispersed phase particle size.
The invention also relates to the conductive compositions of the method and articles made from the conductive compositions of the method.
2. Brief Description of the Related Art
Automobile manufacturers have for a number of years investigated the use of plastic body panels to replace stamped sheet metal panels. The motivation for the replacement has included weight reduction in addition to enhanced performance through elimination of dings and corrosion of the panels.
In the automotive assembly process, it is often desirable to assemble plastic panels and metal body panels onto the automotive frame in the same operation. An undercoating is subsequently applied through an electro-deposition process to afford corrosion resistance to the metal components. Subsequent to this process, paint is applied through an electrostatic process to insure a high transfer rate of the paint onto the panels. Each of these processes involves a baking step at elevated temperatures, often in excess of 180.degree. C. and the high temperatures have been partly responsible for the limited success of plastics in these applications.
Plastic components are in general not sufficiently conductive for electrostatic paint processes. It is known in the art, however, that conductive additives can be formulated into the resin composition to increase the conductivity of the resin. These conductive additives are generally expensive, difficult to handle, and often adversely affect other critical properties such as ductility. Optimization of the quantity of conductive additive necessary for a particular application is desirable to avoid these and other adverse affects.
It is therefore apparent that a need continues to exist for methods of making conductive thermoplastic compositions.